Nonbonded interatomic potential functions for intermolecular interactions in amino acids and peptides are to be obtained, primarily from observed crystal structure and molecular dimer structure data already available in the literature. The criterion of accuracy is the achievement of threshold level fits to the observed data. The observed data are to be supplemented by quantum mechanical calculations of the molecular electric potential and of dimerization energies. The results of these calculations are to be used to assist in the assignment of net atomic charges and lone-pair electron site charges, and in modelling the hydrogen bond interaction. The intermolecular potential functions are to be required to reproduce the structures of water dimer and ice, and also crystalline hydrate structures. These functions are designed to be suitable for use in the calculation of protein conformation and hydration, and the energy and geometry of protein-substrate interaction.